I really dont think it could learn every move because how can it learn spacial rend, roar of time, shadow force, judgement, leech seed, quash and a lot more it can't learn these moves so what makes mew so special is gone due to the fact that it can't literally learn every move in the game.
No. That would be insane. Mew can not learn every move, but it can learn every TM and HM move, every Move Tutor Move, and a fair bit of transfer moves as well. So it can't learn every move, but it can learn every move that you could possibly teach it.